This invention relates to positionable transducer mounting structures and driving systems therefor, and particularly to such structures and systems providing for sweeping motion of the transducer laterally to an elongated track upon a record medium surface.
Co-pending U.S. patent applications Ser. No. 668,571, AUTOMATIC SCAN TRACKING by Richard Allen Hathaway; Ser. No. 669,047, AUTOMATIC SCAN TRACKING by Raymond F. Ravizza et al; Ser. No. 677,815, METHOD AND APPARATUS FOR PRODUCING SPECIAL MOTION EFFECTS IN VIDEO RECORDING AND REPRODUCING APPARATUS by Richard Allen Hathaway et al; Ser. No. 677,683, TRANSDUCER ASSEMBLY VIBRATION SENSOR by David Edward Brown; and Ser. No. 668,651, POSITIONABLE TRANSDUCER MOUNTING STRUCTURE by Richard Allen Hathaway, disclose various forms of apparatus in which a positionable element, particularly a piezoelectric (bimorph) bender assembly, is mounted to support a magnetic transducing head for sweeping motion laterally to a recorded track on a magnetic record medium. Some of the material from these applications is incorporated by transcription hereinbelow to aid in the understanding of the background of the present invention. Briefly, however, it may be said that under certain circumstances, as when adapting the basic structure for "P.A.L." or European television systems, rather than for the "N.T.S.C." or U. S. type systems, in which the structures were first employed, certain difficulties arise from the fact that the head in its sweeping pivoting motion across the record medium, bears first on one side at one extreme of the sweep, then squarely, in the middle of the sweep, and then on the other side at the other extreme of the sweep. At the sweep extremes, the head-to-record medium contact is less, resulting in decreased signal coupling, termed "zenith error".
In addition, it has been found that if care is not taken in attaching the positionable element to its support, azimuth errors are often introduced as a result of the gap of the magnetic head being angularly displaced or skewed from its normal transverse orientation to the longitudinal dimension of the recorded track. Azimuth errors reduce the capability of the system in handling signals of short wavelengths.
Further details of the problem and of its solution will be better understood after reading the following excerpts from various of the above-mentioned patent applications, which material has not yet been elsewhere published.
Accordingly, it is an object of the invention to provide an improved mounting and driving system for a magnetic transducing head sweeping laterally of a track upon a record medium, wherein predetermined orientation and azimuth of the head with respect to the track may be controllably maintained.